1. Field of the Invention
The present invention is related to a monitoring apparatus of a vehicle for recognizing road and traffic conditions around the vehicle based on distance images.
2. Prior Arts
With increased number of vehicles and with increased number of traffic accidents, the conception of Advanced Safety Vehicle (ASV) is becoming one of primary strategies in designing a vehicle. In particular, ASV raises the intelligence level of a vehicle through the state of the art electronic technologies. In recent years, various safety devices such as issuing an alarm to inform a vehicle driver of a likelihood of collision, stopping a vehicle, decreasing or increasing the speed of the vehicle by detecting a vehicle traveling ahead or an obstacle through a television camera, a laser-beam radar or the like, have been proposed.
The inventor of the present invention, in Japanese Patent Application Laid-open No. Toku-Kai-Hei 5-265547, discloses a technique in which pictures taken by two stereoscopic cameras are converted into distance images, these distance images are divided into lattice-like small regions at an interval of 8 to 20 picture elements and solid objects are detected for each small region.
This prior art is primarily intended to be used for detecting obstacles in highways or roads for motoring and therefore the roughness of pictures this like, i.e., 8 to 20 picture elements per small region, is at a permissible level because the size of obstacles can be considered to be relatively large.
However, when the subject vehicle travels on narrow or crowded street roads, in order to judge a possibility of collision or contact with an obstacle lying on the road with high precision, it is necessary to detect a correct position of the obstacle and its more detailed configuration such as an unevenness of the surface of the object or protuberances or indents of the obstacle as well. To cope with a situation like this, the distance image must be divided at a finer interval than 8 to 20 picture elements. On the other hand, such a rough interval as 8 to 20 picture elements tends to incur erroneous detections due to noises included in the image.